The present invention relates generally to the art of integrated motor and drive systems and, more particularly, to a motor with an integrated drive unit and a shared cooling fan.
This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Motors have broad application in industry, particularly when large horsepower is needed. Typically, power in the form of AC current provided by a utility is not suitable for end use in consuming facilities. Thus, prior to end use, power delivered by a utility is converted to a useable form. To this end, a typical power “conditioning” configuration includes an AC-to-DC rectifier that converts the utility AC power to DC across positive and negative DC buses (i.e., across a DC link) and an inverter linked to the DC link that converts the DC power back to three phase AC power having an end-useable form (e.g., three phase, relatively high frequency AC voltage). A controller controls the inverter in a manner calculated to provide voltage waveforms required by the consuming facility. The inverter includes a plurality of switches that can be controlled to link and delink the positive and negative DC buses to motor supply lines. The linking-delinking sequence causes voltage pulses on the motor supply lines that together define alternating voltage waveforms. When controlled correctly, the waveforms cooperate to generate a rotating magnetic field inside the motor stator core. In an induction motor, the magnetic field induces a field in motor rotor windings. The rotor field is attracted to the rotating stator field and thus the rotor rotates within the stator core. In a permanent magnet motor, one or more magnets on the rotor are attracted to the rotating magnetic field. The rectifier, inverter, and control circuitry are commonly referred to as a motor drive unit.
The use of integrated units where the motor drive is integrated with the motor to create an “integrated motor and drive system” has become more widely used. One advantage of such systems is their compactness and ease of installation into a larger industrial or other application, due largely to the close proximity of the drive to the motor. Generally, the drive is disposed on the motor or arranged in an integral housing with the motor.
One issue arising from the integrated motor and drive system arrangement involves providing adequate cooling flow to dissipate the collective heat generated by the motor and drive. Previous techniques for providing cooling for an integrated motor and drive involve providing independent cooling for the motor drive or diverting a portion of the cooling flow from the motor fan to impinge upon the motor drive or a heat sink associated with the motor drive. These solutions add cost to the motor drive assembly and sometimes fail to provide adequate cooling, as only a portion of the cooling flow is employed.
Another disadvantage is that heat sinks applied to motor drive components typically provide a cooling effect that is substantially uniform over its surface area. This is due to the even, or regular, distribution of the heat transfer fins on the face of the heat sink. This design limitation largely ignores the reality in motor drives that certain power and other electronic components generate large amounts of heat, while other devices may generate only small amounts. Thus, a traditional heat sink requires that either the power components be evenly distributed over the heat sink surface with regard to their power generating capabilities, or that a large enough heat sink is used to compensate for “hot spots” created by the physical arrangement of power components to provide for adequate cooling of the largest expected localized areas of heat generation.